This invention relates generally to devices for measuring radiation energy and specifically to devices for measuring the radiation from the sun. An example of representative prior art is U.S. Pat. No. 3,891,326 relating to a multi-channel sun photometer. As is typical of prior art, the device of U.S. Pat. No. 3,891,326, must be properly aligned, depending on the momentary position of the sun, to provide accurate readings.